Raised bogs are found in primarily lowland areas. Water logging & anaerobic conditions result in slow decomposition of plant material & accumulation of peat. As a result, a raised dome-shape is formed above the surrounding land, which is rain-fed or ombrotrophic.
- Site: High rainfall & low temperatures. Lowland areas <150 metres
- Soil: Water-logged & oxygen-limited. Accumulation of peat to form an elevated dome region
- Main species: Sphagnum moss, heather, cross-leaved heath, bog cotton, deergrass, sundews, white beaked sedge
- UK: 6,000 ha
- NI: 2,000 ha
- Raised bog develops on lowland areas below 150 metres.
- They form on waterlogged soils which have shortage of oxygen. Such areas include the head of estuaries, along river flood-plains & in topographic depressions.
- Due to the accumulation of peat a shallow, curved dome-shape is formed which is higher than the surrounding land. The area surrounding the dome is typically mineral soil or shallow peat. The depth of the peat can exceed 13 metres.
- High rainfall & low summer temperatures support the formation of raised bogs by maintaining high groundwater levels. The surface of raised bogs may support a mosaic of pools, hummocks & lawns (NIEA, 2003), which have water regimes that support different plant species.
- Due to the acidity & deficiency of plant nutrients, plant diversity is generally low but specialized communities dominate, including Sphagnum moss species & cotton grasses Eriophorum spp. Rarer species are also supported such as Sphagnum pulchrum & S. imbricatum, bog rosemary, cranberry & great sundew.
- Raised bogs support various plant communities defined by the NVC of Great Britain: M2 Sphagnum cuspidatum/recurvum & M1 S.auriculatum bog pool communities, M17 Scirpus cespitosus – Eriophorum vaginatum blanket mire and M18 Erica tetralix – Sphagnum papillosum raised & blanket mire. Further communities are supported on human-disturbed lowland raised bogs: M15 Scirpus cespitosus – Erica tetralix wet heath, M20 Eriophorum vaginatum blanket & raised mire, M25 Molinia caerulea – Potentilla erecta mire and W4 Betula pubescens – Molinia caerulea woodland (NIEA, 2003)
Current Status in UK & Northern Ireland
- UK lowland raised bog has declined: decrease in undisturbed surface by 94% from 95,000 ha to 6,000 ha.
- Northern Ireland has a rich resource of lowland raised bog but they are typically smaller than those in other areas of the UK & ROI (Hammond, 1981; NIEA, 2003).
- §The NIPS (Cruickshank & Tomlinson, 1988) estimated that of the original lowland bog resource of 25,196 ha, only 2,270 ha (approx. 90%) remained intact. Field surveys by EHS staff showed that 2,000 ha remains, of which 1,600ha is ‘near natural’ but 400ha is in a ‘degraded state’, supporting less than 10% Sphagnum moss cover (NIEA, 2003).
- Human activities which have resulted in the decline of lowland raised bog include hand-cutting for fuel, mechanised peat extraction & drainage to enhance productivity for agriculture & forestry (NIEA, 2003)
- The NICS (2000) reports a decline in the condition of lowland raised bog.
- Caldanagh Bog
- Dunloy Bog (Main Valley Bog )
- Frosses Bog
- Garry Bog